$α_s$ at Zinnowitz 2004

A review of measurements of $\alpha_s$ is given, representing the status of April 2004. The results prove the energy dependence of $\alpha_s$ and are in excellent agreement with the expectations of Quantum Chromodynamics, QCD. Evolving all results to the rest energy of the $Z^0$ boson, the world average of $\alpha_s(M_Z)$ is determined from measurements which are based on QCD calculations in complete NNLO perturbation theory, giving $\alpha_s(M_Z) = 0.1182 \pm 0.0027 .$